1. Field of the Invention
The present invention relates to yarn tensioning devices. In particular, the present invention relates to a yarn tensioning device having three pairs of tension disks, each with different spring rates, so that the pressure the three pairs of tension disks exert on the yarn is singularly and simultaneously adjustable.
2. Discussion of Background
Yarn tensioning devices have been known in the art since at least 1919. (See U.S. Pat. No. 1,385,189 issued to Pigeon on Jul. 19, 1921.) During twisting or cabling operations, two strands of yarn are brought together and twisted or wrapped, thus forming a two-ply cabled yarn. Both ends of the yarn follow a different path until they meet in the twisting operation, but it is imperative that the tensions of each yarn be balanced during the cabling process in order to obtain a regular folded yarn. The end coming from the creel makes the balloon and determines the tension of the process. The tension of the yarn coming from the pot lid must then be regulated and controlled to match the tension of the creel yarn.
Various tensioning devices have been used in the art, having two and three pairs of discs to apply tension to the yarn or applying tension by magnetically controlled tensioning devices. However, each device in the prior art has had its deficiencies. The magnetic devices are too expensive to be a cost effective way of controlling the tension in the yarn coming from within the pot lid.
The prior art tensioning devices, having two or three pairs of tension discs, come in two basic forms. The first form is disclosed by Heizer in U.S. Pat. No. 2,629,561 which issued Feb. 24, 1953, and by Mackie, et al. in Italian Patent Number 550,892 which issued Nov. 10, 1956. In these patents, the inventors disclose a device having two pairs of tension discs that can both be adjusted at a single time. However, the pressure applied to the yarn by both of these tension discs is controlled by a single spring. Consequently, as it enters the tension discs, the yarn experiences the same pressure from each pair of disks, and inevitably the maximum pressure and subsequent tension on the yarn is applied by the first pair of disk it enters. For the yarn to experience its greatest pressure immediately upon entering the first disk may not have been a problem in the prior art, as the tensions experienced by the yarn only averaged 100 grams. The present cabling systems, however, operate with tensions sometimes in excess of 750 grams. As a result, if the yarn were to experience an immediate pressure that provided a tension of 750 grams, the yarn would bunch, or it is possible that its filaments would begin to separate and tear.
Therefore, it was necessary to provide a tensioning device that supplied the pressure needed to obtain the tension for today's operating parameters. A device constructed by Volkmann has three pairs of tension discs, each having different spring rates, that apply pressure to the discs such that the yarn experiences an incremental pressure as it is decelerated or tensioned sequentially by the three pairs of disks. However, as these devices are used in the manufacturing facilities, technicians are required to adjust and modify the tension applied by the devices. As a result, the tensioning devices become inconsistent over time when compared to each other. A tension device on one cabling system may provide tension to the yarn that is equal to the next, but the manner in which the tension is applied, i.e., the incremental nature, may be completely different. The first pair of disks in one tensioning device may apply 300 grams of tension, whereas the first pair in a second device may apply 100 grams, although both may apply a total of 700 grams of tension overall. Therefore, it was possible to have a cabling system that gave the appearance of operating in conformity with the next one, but which produced cabled yarn at different qualities due to the incremental nature of the pressure applied to the yarn.
Furthermore, when changing "runs," or the type of yarn that is cabled, different tensions must be applied to different type yarns. Therefore, when changing "runs," a technician is required to adjust the three tension posts individually, check the new settings with a tensiometer, and then repeat this step until the desired tension is found. It is common to have a number of cabling systems running side-by-side, each of which requires the same time-consuming operation of individually adjusting the three tension posts at each station. Additionally, during this operation a large amount of yarn is wasted, due to the fact that yarn is passing through the machine during each adjustment operation. Furthermore, because the discs rotate, broken or loose filaments tend to become entrapped in the device, causing wear and requiring additional labor to clean the device.
Therefore, there is a need for a tensioning device that applies incremental degrees of pressure to the yarn as the yarn is decelerated through the tensioning device. There is also a need for a tensioning device that maintains incremental degrees of pressure even after technicians have modified and adjusted the spring posts. Furthermore, there is a need for a tension device in which all of the tensioning posts are adjusted simultaneously, thus eliminating the possibility of changing the incremental nature of the pressure and providing a quicker and easier adjustment to the tensioning device, so that down time and wasted yarn between product "runs" is minimized.